Method and means of transmitting pictures



Jul 5 1927.

y E. BELIN METHOD AND MEANS OF TRANSMITTING PICTURES Filed Feb. 9. 1925 Patented July s, 1927.

PATENT OFFICE.

nnomum 31mm, or rams, runner.

METHOD AND MEANS OF TRANSMITTING PICTURES Application (fled February 9, 1925. serial No. 8,022.

The invention relates to the transmission of pictures, and particularly to .the transmission of pictures which are composed in whole or in part of half tones, that is, tones including all possible degrees between black and white indicating all graduations of the illumination of an object between maximum and minimum. This definition, of course, includes any variations however abrupt such as occur in line drawings, printed matter, manuscript and the like, in which there is substantially no intermediate tone. The invention is therefore particularly suitable to the transmission of photographic pictures in which all gradations of illumination of the original object are to be reproduced at the receiving end, either as a positive or negative, and with or without certain compensations :or corrections. Generally the invention includes a transmitting station with means for generating a carrier current to be usedin the transmis sion either over a line or by radiation through suitable radio transmitting and re ceiving apparatus, and a modulating appa ratus adapted to impose modulations upon the carrier current which are a function of, or correspond to, variations in the illumination of successive points of the object the picture of which it is desired to transmit; and a receiving station at which is located apparatus adapted to eitect variations in the illumination of successive points on a receiving surface in accordance with the F modulations of the carrier current such that the variations of illumination of successive points on the receiving surface will be pro portional to the variations in illumination of the corresponding successive points of the object the picture of which is being transmitted, in all gradations of tone.

The inventionalso contemplates means at the receiving end for inverting 01' vary- 0 ing the proportional relations, as where the image is to be inverted or made negative or the proportions varied to compensate for defects in the quality of the photograph to be transmitted, variations in the density of the current, or the susceptibility or characteristic of the modulation, detecting or responsive means.

My invention is illustrated in the accompanying drawings in which:

Figure 1 is a diagram of a transmitting system embodying the invention; and

' or other suitable means,

Figure 2 is a detail view in the form of an enlarged cross section through the transmittilng microphone and a relief photograp Referring now to Figure 1 which is a dia grammatic representation of a preferred embodiment of the invention, A and B are the transmitting and receiving stations, respectively, connected by a suitable transmission line consisting of the conductors 1 and 2. At the transmitting station, 3 is the means for supplying the carrier current which is connected with the line circuit through the modulating means 4 for modulating the carrier current'in accordance with the illumination of successive picture of which is to be transmitted. At the receiving station B there is provided a receiving surface 5 successive points of which are illuminated by a light beam 6 arranged to have its intensity varied by means of a light modifying screen 7 in response to movements of a mirror 8 of an oscillograph or mirror galvanometer. 9 having-its energizing circuit operatively connected in the line 1-2 and arranged to respond rent oscillations and the modulations thereof so as to produce, through the medium of the screen 7, variations in intensity of the light beam corresponding to the modulations. The response of the mirror galvanometer to the carrier current oscillations is such that the mirror actually follows the oscillations'of. the carrier current, that is, there is a complete oscillation of the mirror for each oscillation of the carrier current, the oscillations varying in amplitude according to the variations in amplitude of the corresponding carrier current oscillations caused by the.

modulation of the carrier current, so that the deflections represent actual instantaneous values of the modulated carrier current and not the average value of the modulated 0scillations as where detection or demodulation is depended upon.

While the generator 3 is here indicated as a mechanically driven alternator or alternating current generator, it is to be under stood that it is symbolic of any known or other suitable form of alternating current generator which may be substituted therefor, and that while the medium of transmission between the sending and receivingstations is here shown as a pair of line wires 12, this means may also be substituted by any known such for example as points of the object, the e to the carrier curin accordance with the variations in thickness of the record, or instead of using a microphone the variations in thickness of the record may be made to effect modulation by varying the constants of the circuits, for instance, inductance and capacity, and thus modulate by changes "of frequency. The variations in translucence of a trans lucent photograph (positive or negating may be operated upon directly to efiect mo ulation by causing a beam of light to pass through the photograph to light sensitive means such as a selenium cell, photo-electric cell, or the like, capable of producing electrical variations in response to variations in light intensity.

In the preferred form of the invention here illustrated, the modulating means is in the form of a microphone operated upon by a. photographic record in relief in which record the variations in thickness at successive points correspond to variations of the illumination of corresponding successive points on the original object.

Since the record to be operated upon must represent in relief the object, a picture of which it is desired to send, with differences in thickness of the relief proportioned to or a function of the illumination of corresponding points of the object in all gradations of tone, it is most convenient to use a photographic record of the bichromatized gelatine type, developed, fixed and hardened in order to withstand wear.

As is well understood, such a record may be prepared from an ordinary photographic negative in which the opacities while not directly proportional to the illumination of the corresponding points in the original object nevertheless are a function of, that is vary in accordance with, variations of such illumination. Thus a bichromatized gelatine print from the negative will when finished according to the well known process be a photographic record of the original object in various degrees of light and shade. The various degrees of light and shade being due to a thickness'of insoluble matter there are on the surface of the gelatine reliefs which exactly translate the opacities of the negative and consequently the variations in light and shade of the original object. Either the variations in li ht and shade or the variations in relief of t is record maybe used to effect the modulating means. The preferred 4 form, here shown, utilizes the reliefs of the record operated upon by an exploring point. The modulating means acted upon by the relief record is the microphone 4 of Figure 1, which device in connection with its relation with the record is shown in detail in Figure 2. Here 10 indicates the photographic record carried by the cylinder 11 which, as shown in Figure 1, is mounted to be rotated before the microphone 4 upon a shaft 12 geared to a feed rod 13 arranged to move the microphone axially of the record.

The microphone consists of a casing 14 in which is fixed an elastic blade 15 which carries a stylus 16 arranged to bear against the photographic record 10. The blade 15 carries on its opposite side a metallic contact plate 17 which bears against a ball 18 of conducting material such as carbon or graphite in the cup 19 of insulating material. The cup 19 is fixed in the casing 14 and is threaded to receive an adjusting screw 20 which passes therethrough into engagement with the ball 18 for the purpose of adjusting the pressure between the same and the plate 17. Electrical connection is made with the ball 18 through the adjusting screw 20, while connection is made with the late 17 through the blade 15 and casing 14 by means of a suitable binding post or screw as indicated at 21. ,Thus with the arrangement described, as the record 10 is moved past the stylus 16 variations in the relief will be translated into variations in contact pressure between the plate 17 and the ball 18 which in turn will be translated into variations in resistance of said contact.

As shown in Figure -1, rotation of the record surface 10 will be accompanied by rotation of the feed screw 13 controlling the movement of the microphone across the rec- 0rd, with the result that there is, relatively, a spiral movement of the stylus 16 over the surface of the record.

At the receiving station is provided a similar cylindrical record holder 22 mounted on a shaft 23 which shaft is arranged at one end to turn and slide in the bearing 24 and at the other end is threaded to engage internal threads in the bearing 25, so that when the shaft is turned the cylinder.22 will be rotated about its axis and at the same time moved longitudinally of its axis in the direction indicated by the adjacent arrow. While the shafts 12 and 23 are here indicated as being driven by handles 26 and 27, respectively, for the sake of simplicity, it is to be understood that the motions of the transmitter and receiver bear a definite time relation to one another, preferably a synchronized relation, which may be obtained by any known or other suitable means, not

eter 9 at the receiving station has its energizing circuit 28 connected in the line circuit 1-2 and its field windings 29 connected with a suitable local source of current 30. A lamp 31 is provided at the receiving station arranged to project a beam 6 against the mirror 8 of a galvanometer and the parts of the galvanometer are so arranged that the mirror will normally reflect the beams 6 through the central portion of the screen 7 and condensing lens 32 to .the surface of the receiving, element 5 carried by the cylinder 22. The lamp 31 may be of any form capable of projecting a well defined beam of light of substantially constant intensity. It is here indicated, by way of example, as an electric light projecting device supplied from a suitable current source 33. To effect the translation of the deflections of the beam 6 into variations of intensity proportional to the maximum throw of the galvanometer mirror, and consequently proportional to the amplitude of the modulated carrier current, the screen 7 is formed of a member which is graduated from substantial opacity at its center 34 to constantly increase in transparency toward each end 35 and 36. This rate of variation from substantially total opacity to substantially perfect trans parency must be such that a given deflection, of the galvanometer will produce an illumination of the receiver proportional to the modulations controlling such deflections. These proportions should be such that the variations in intensity of the beam will be proportional to or a function of the variations in illumination of successive points on the object the picture of which is being transmitted.

In operation, a relief photographic record 10, prepared as hereinbe'lore described, is placed on the cylinder 11 at the transmitting station A, and at the receiving station a piece oi. photographic paper 5 is placed on the cylinder 22. Both cylinders are now rotated in synchronism. As the cylinder 11 rotates, successive points of the record surface are brought into engagement with the stylus 16 ot the modulating microphone 4 which causes the variations in relief to be trans lated into variations in pressure and consequently variations in resistance between the contact plate 17 and ball 18. As the line circuit 12 and the generator 3 are connected in series with the microphone,

these variations in resistance are translated into modulations of the carrier current passing over the line 12. The carrier current passing through the energizing circuit 28 of the galvanometer causes the mirror to oscillate in unison therewith and with an ampli tude varying in accordance with the modulations. As the beam 6 is oscillated across the center of the screen b the oscillations of. the mirror 8, responding in frequency to the frequency of the carrier current, carrier current oscillations of low amplitudes will cause the beam to oscillate only a short distance either side of the center with its points of reversal or pause and lowest rate of movement near the darker portions of the screen, while high amplitudes Will cause the beam to oscillate a greater distance either side of. the center, bringing its points of reversal, or points of slowest movement into the lighter or more transparent portions of the screen. However, no substantial or practical effect is produced on the receiving surface during the oscillation of the mirror, but only at its points of reversal. Thus the beam in passing through the screen 7 is varied in intensity in accordance with the amplitude of oseillation of the mirror 8. This beam of Varying intensit is condensed by means of the optical con enser 32 to a point at the surface of the sheet of photographic paper 5.

As the receiving surface 5 is moved to present successive points to the luminous point 37 in synchronism with the presentationot corresponding points on the record 10 to the microphone stylus 16, the illumination of the receiving surface will be varied at successive points in accordance With the variations in illumination of the original object at corresponding successive points. Thus, the photographic paper receives a latent image 38 which upon development will be a'repre sentation of the original obj ect in all its gradations of tone.

'It will be understood that only half of the movements of the galvanometer may be made use of by simply'covering one half of the screen 2.

In preparing the screen 7', account should be taken of the fact that the opacity or photographic density in the usual photographic record is logarithm of the quantit of light received. To produce a screen witi opacities varying from the center to the sides in accordance with this law a photographic plate may be given an exposure continuously increasing in time from the sides to the center at the rate of O, 1, 2, 4:, 8 etc. which, when the plate is developed, Willresult in a negative in which the opacity will vary in the order 0, 1, 2, 3, 4, etc. in an'arithmetical progression. Y

The graduated screen 7 may be obtained by other methods as by photographing a white cylinden illuminated from the side, exposing a photographic plate through a Wedge of smoked glass, or exposing the plate through a rotating window or shutter opening having a geometric curve. It will be understood that where these methods are proportional to the I til used, the rate of variation ofopacity may be varied by varying the angle of incidence of light on the cylinder, or varying the angle of the wedge of sn'iolied' glass.

\Vith such adjustments it is possible to make the screens operate to compensate for variable factors such as the quality of the photograph to be transmitted, the density of the carrier current, the susceptibility of the galvanometer, etc. For exuu 'ple, the screens may be so graduated as to make the received photograph more or less contrastive than the photograph transmitted; different screens may he graduated so that one will produce the same etl'ect with a car rier current of a given normal density as does another screen with a carrier currentof a ditt'erent given, normal density, or if the susceptibility or characteristic of the galvanometer is such as to tend to produce at the receiver an image more or less contrastive than the original photograph, or with tones varying at a different rate, compensation may be effected by suitable variation of the tone graduation of the screen. (onditions may also be moditied by vary ing the intensity of the light beam at the receiver.

It will be seen from the foregoing that with the system herein disclosed, it is possible to obtain the following equations in its operation:

It. The variations in tone of the photograph being transmitted are proportional to or a function of the variations in illumination of the original object photographed.

2. The variations in relief of the relief photographic record vary with or area function of the tone variations of the photograph being transmitted.

3. The variations in pressure between the microphone contacts (and consequently its resistance) are a function of the variations in relief of the relief photographic record.

at. The modulation of the carrier current is av function of the variations of pressure between the contacts of the microphone.

5. The amplitude of the deflect-ions of the galviinometer at the receiving station is a function of the modulation.

6, The effect of the screen on the beam to vary its intensity is a function of the amplitude of the deflections of the galvanometer.

7. The variation in tone of successive points on the photograph received is a function of the variation in density of the beam.

Thus, the variations in tone of successive points on the photograph received are a function of the variations in tone of all corresponding points on the object a photograph of which is being transmitted, so that the transmitted photograph of the object will record all gradations of tone of the original.

The term microphone is herein used to designate a variable resistance device of the microphone type, and not a device operating as a microphone in the strict sense of the term, that is, not a device for translating sound into electrical variations. The variable resistance or microphone here used differs from the ordinary telephone microphone-in that it is not actuated by a freely vibrating diaphragm but by motion transmitting means between it and the actuating record such that all variations in resistance and consequently all modulation is the direct result of the actuating force. This difference is essential as the modulations here used are not necessarily always oscillatory in character. That is, in the modulations, the varying values are not symmetrical ot. a given mean value as in. sound modulations wherev each positive wave is followed by a negative wave of corresponding magnitude, or an increase above a given mean value is followed ,by a return to the mean and a corresponding deerease below the mean. To the contrary, the modulations here transmitted consist of many 'ariations that do not pass through the mean value so that a free oscillating diaphragm or responsive member would be detrimental in that it would tend to oscillate symmetrically of a given mean point or repeat each variation in the opposite direction instead of following the asymmetrical modulations.

While I have herein shown and described a specific embodiment of my invention for the purpose of disclosure, it is to be understood that the invention is not limited to such specific embodiment but contemplates all such modifications and variants as fairly fall Within the scope of the appended claims.

Having thus described my invention, what I claim is 1. Means for modulating a current with non-oscillatory variations comprising a variable resistance of the carbon button microphone type having a stationary button and a pressure button in engagement therewith carried by an aperiodic support responsive to the modulations to be impressed.

2. Means for modulating a current in accordance with continuous variations of light and shade through successive points in a picture, comprising a variable resistance of the carbon button microphone type having a stationary carbon electrode, a pressure electrode in engagement therewith, an aperiodic support for the pressure electrode, actuatin means operable in proportion to the variations in light and shade of the successive points in the picture, and resilient connecting means between said actuating means and the support,

In testimony whereof I aflix my signature.

EDOUARD BELIN. 

